compression test

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Youngcummins
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Posts: 309
Joined: Mon Jun 29, 2009 7:51 pm
Location: Terre haute, IN

compression test

Postby Youngcummins » Fri Nov 30, 2018 8:58 pm

Hi Gents,

Thought i would check the compression on my s10 with a 81 luv c223. Looks to be a little low. Thought I would make a video to brush up on some editing skills. What are your guys thoughts?

Other than eBay is there a good place to get a sleeve and piston kit?

https://youtu.be/_8rLb8fkQRE
My rig
1996 Ram 2500 Cummins, 414K miles
2000 S10 reg cab long bed with a 81 LUV c223 5 speed, the runt of the fleet, but the most driven.
2003 Jetta GLS TDI 5sp, 53mpg!!!

2sk8
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Posts: 209
Joined: Thu Apr 17, 2008 2:59 am
Location: California
Isuzu vehicle(s): 91 Isuzu Pick up converted to diesel

Re: compression test

Postby 2sk8 » Sat Dec 01, 2018 11:17 am

I seen worst numbers. Is that the harbor freight gauge?

It looks like it. That gauge is not that accurate so your numbers could be higher. Best gauge to use is the liquid type, a lot more accurate.

Also did you do a valve adjustment before the compression check? If not then your compression numbers will be higher than what you are seeing.

Here is a post from the forum about compression numbers:

Compression numbers?

I've seen numbers from 260s all the way to 430s

when there all 400+ you got a good one.

375 for an average or higher OK, but going to struggle to start in temps under 25F.

get down to 350 and under for an average it will be hard to start in cold temps WITH GOOD GLOWS

300 and under you need a top notch BAT and glows to get it started in the cold....
let alone the hp will be 50% under the OE numbers or worse.....so MPG will suffer a good bit..

http://www.isuzupup.com/viewtopic.php?t=17769

About sleeves and pistons from ebay:

There is the chinese chrome liners but those are hard to find a machine shop that can install them right because it's a difficult boring on the top.

I got those chrome liners installed and they are very good, will last you for ever, they are super hard but you NEED cast iron rings only or you'll ruin them.

A lot o people get them and install regular rings on them and they get ruined.

If you need a set of original pistons, I have a brand new set (Original), made in Japan. The real deal. If the price is right and willing to let them go.

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Halden
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Joined: Thu Mar 29, 2012 5:20 pm
Location: Everertt, WA
Isuzu vehicle(s): 1983 Diesel LS Long Bed 4x4

Re: compression test

Postby Halden » Sat Dec 01, 2018 1:14 pm

Compression is a bit of a subjective measurement... There are variables you need to factor in, ambient temperature, humdity, altitude, battery voltage, health of starting system and other things. What's more important is that they are even.

They can't meausre compression on large bore engines. It's just too impractical so you can figure at least if the cylinders are even by finding an electrical reference to #1 tdc and then scoping current draw from the starter and checking for an even wave... Bottom line is your numbers seem okay IMO. Cummins doesn't even publish compression figures in quick serve as far as I know... At least for 90% of their stuff... On one of Kubota's small engines they specify something well over 500 new. And then after use they specify something well below 500 as fine. Isuzu doesn't specify they just say 441psi at 200 RPM... Is your starter turning the engine that quickly?

Stick your hand under the draft tube when warmed up. Do you feel a pretty strong steady draft a few inches away? A *puff puff puff*? Is it billowing or just whispering blowby out? That's probably a better way to assess... And even better - oil consumption and performance. How are they?
It's not pronounced "Ih-soo-zoo", it's pronounced "It-screws-you"
83 LS Long Bed Diesel
64 Chevy C20 w/ 283 & 4 speed.
05 Sonata with a standard

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Youngcummins
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Posts: 309
Joined: Mon Jun 29, 2009 7:51 pm
Location: Terre haute, IN

Re: compression test

Postby Youngcummins » Sat Dec 01, 2018 9:03 pm

the reason for asking is that the truck has progressively gotten harder to start in colder temps. a few years ago and maybe 10k miles I had to pull the head and replace the guides due to them being too loose and letting a valve seal fail and cause a valve to not fully close. At the time I bought the harbor freight kit in the video and it showed 400psi on all cylinders but 3, it was around 380. The pistons were very sloppy in the bores, seems low on power, and seems to all be pointing towards needing a freshening. Ive changed the glow plugs within the last year, its a custom 12 volt system, valves should be close having only 10k miles on this adjustment, but haven't confirmed. The only thing I haven't done is had the injectors pop tested to make sure they have the right pop off pressure.

Thanks for the inputs
My rig
1996 Ram 2500 Cummins, 414K miles
2000 S10 reg cab long bed with a 81 LUV c223 5 speed, the runt of the fleet, but the most driven.
2003 Jetta GLS TDI 5sp, 53mpg!!!

User avatar
Halden
Regular Member
Posts: 2715
Joined: Thu Mar 29, 2012 5:20 pm
Location: Everertt, WA
Isuzu vehicle(s): 1983 Diesel LS Long Bed 4x4

Re: compression test

Postby Halden » Mon Dec 10, 2018 2:57 pm

For kicks I decided I would test my compression... I had some pretty Crazy numbers... starting from cylinder 1 - 320 320 400 380. Tremendously uneven... One of the biggest give aways is the sheer amount of blowby the truck produces...
It's not pronounced "Ih-soo-zoo", it's pronounced "It-screws-you"
83 LS Long Bed Diesel
64 Chevy C20 w/ 283 & 4 speed.
05 Sonata with a standard